OnePager Pro and Express have several elements such as the title, time axes, rows and swimlanes, headers and footers, and the legend, which can be repeated across multiple pages in your report.
On the OnePager Page Layout tab, there is a section called Repeating Elements, which contains five of these options:
When you turn these boxes on or off, you can control whether these elements appear on all pages, or just the first page. With all these boxes checked, all of the elements will appear on all of the pages in the multi-page project view as shown below:
If you uncheck the title, rows/swimlanes, and time axis boxes, the four pages will look like this:
Repeating the legend is a more complex option and is configurable under Home->Project View Properties->Legend.